This invention relates to a magnetic shielding member or device capable of efficiently protecting a magnetic recording member against the adverse effects of external magnetic fields.
Recently, cash cards and credit cards, etc. are used in many banks and department stores and a person who utilizes such a card normally carries it with him. Furthermore, as a result of the tendency of office automation, floppy discs and magnetic tapes are abundantly used in many offices so that persons who utilize such discs or tapes always carry them.
Further, permanent magnets are used in many kinds of every day articles and articles in offices, for example clasps of handbags, magnetic plates, various therapeutic or health promoting devices, and toys. Permanent magnets having a strength of several thousands of gausses are used in articles of the type described above.
Magnetic information recorded in a magnetic recording member are alternated or erased by the strong magnetic field of such powerful permanent magnets, thus causing misoperation of an automatic cash pay-out machine installed in banks and of office automation machines. Various types of protective casings for containing or covering magnetic recording members have been proposed for the purpose of preventing the troubles described above. For example, a casing made of magnetic material and a casing made up of a lamination of a layer of crystalline magnetic metal having a high saturation magnetic flux density and a layer of amorphous metal having high permeability have been proposed. Each of them does not manifest the desired magnetic shielding effect. In addition, it is necessary to use special and expensive metals.